Ubuntu equivalent of mkinitcpio.conf

Question

I have a sh script that should be executed during system boot, as I understand before graphic driver modules are loaded.

Probably this is not relevant for the answer, but this script serves for PCI passthrough of a GPU in the special case a system has two identical GPUs sharing the same id, to override the driver assignment only on one of the two GPUs.

For arch linux systems, a wiki says that one should:

Edit /etc/mkinitcpio.conf:
Add modconf to the HOOKS array and /usr/local/bin/vfio-pci-override.sh 
to the FILES array.
Edit /etc/modprobe.d/vfio.conf:
Add the following line: install vfio-pci /usr/local/bin/vfio-pci-override.sh
Regenerate the initramfs and reboot.

What is the Ubuntu equivalent of mkinitcpio.conf and how should it be modified in this case? Just in case, the script is the following:

#!/bin/sh

DEVS="0000:01:00.0 0000:01:00.1"

if [ ! -z "$(ls -A /sys/class/iommu)" ]; then
    for DEV in $DEVS; do
        echo "vfio-pci" > /sys/bus/pci/devices/$DEV/driver_override
    done
fi

Answer 1

The package is called (man page) initramfs-tools (see wiki: wiki.ubuntu.com/Initramfs).

initramfs-tools - an introduction to writing scripts for mkinitramfs

initramfs-tools has one main script and two different sets of subscripts which will be used during different phases of execution. Each of these will be discussed separately below with the help of an imaginary tool which performs a frobnication of a lvm partition prior to mounting the root partition.

Configuration:

/etc/initramfs/initramfs.conf

Mind that ...

/etc/initramfs/conf.d/

can be used for configuration files and

/etc/initramfs/conf-hooks.d/

for adding hooks. To rebuild you can use ...

 update-initramfs -u